An electrostatic discharge (ESD) event injects a significant amount of charge through an input terminal of a circuit (often, an integrated circuit). Without some sort of protection, the high currents and voltages associated with the ESD event may damage the circuit. To protect the circuit, the ESD event may be detected and a signal may be created in response. The signal may be applied to a switch or other mechanism (i.e., an ESD clamp) to direct enough ESD charge to ground to prevent circuit damage.
Conventional power supply rail-based ESD protection mechanisms use slew rate sensitive sensors (ESD triggers) which apply fixed RC time constants to activate, during ESD events, a set of voltage controlled current switches called ESD clamps or switches, coupled across the power supply rails (e.g., vcc to ground). Fixed RC time constant ESD triggers may erroneously activate the ESD clamps during excessive power supply noise, affecting the power supply value of the protected circuit and thus its performance parameters (for example access time for a memory integrated circuit).